Handling two WebException's properly

问题

I am trying to handle two different WebException's properly.

Basically they are handled after calling WebClient.DownloadFile(string address, string fileName)

AFAIK, so far there are two I have to handle, both WebException's:

The remote name could not be resolved (i.e. No network connectivity to access server to download file)
(404) File not nound (i.e. the file doesn't exist on the server)

There may be more but this is what I've found most important so far.

So how should I handle this properly, as they are both WebException's but I want to handle each case above differently.

This is what I have so far:

try
{
    using (var client = new WebClient())
    {
        client.DownloadFile("...");
    }
}
catch(InvalidOperationException ioEx)
{
    if (ioEx is WebException)
    {
        if (ioEx.Message.Contains("404")
        {
            //handle 404
        }
        if (ioEx.Message.Contains("remote name could not")
        {
            //handle file doesn't exist
        }
    }
}

As you can see I am checking the message to see what type of WebException it is. I would assume there is a better or a more precise way to do this?

Thanks

回答1:

Based on this MSDN article, you could do something along the following lines:

try
{
    // try to download file here
}
catch (WebException ex)
{
    if (ex.Status == WebExceptionStatus.ProtocolError)
    {
        if (((HttpWebResponse)ex.Response).StatusCode == HttpStatusCode.NotFound)
        {
            // handle the 404 here
        }
    }
    else if (ex.Status == WebExceptionStatus.NameResolutionFailure)
    {
        // handle name resolution failure
    }
}

I'm not certain that WebExceptionStatus.NameResolutionFailure is the error you are seeing, but you can examine the exception that is thrown and determine what the WebExceptionStatus for that error is.

来源：https://stackoverflow.com/questions/2650758/handling-two-webexceptions-properly

标签

exception-handling

webclient

downloadfile

webexception